subtractive machining
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AbstractHybrid manufacturing processes are known for combining the advantages of additive manufacturing and more traditional manufacturing processes such as machining to create components of complex geometry while minimising material waste. The trend towards lightweight design, especially in view of e-mobility, gives aluminium materials an important role to play. This study examines the use of aluminium alloys in laser metal wire deposition (LMWD) processes with subsequent subtractive machining, which is considerably more difficult due to the different process-related influences. The investigations are focussed on the influence of the differently controlled laser power on the shape accuracy, the microstructure, and the hardness of the AlMg5 test components after the LMWD process with subsequent subtractive machining by turning. The long-term goal of the investigations is to increase the stability of the hybrid production process of AlMg5 components with defined dimensional accuracy and mechanical properties.

AbstractAdditive manufacturing (AM), particularly laser-based powder bed fusion of metals (LPBF), enables the fabrication of complex and customized metallic parts. However, 20–40% of the total manufacturing costs are usually attributed to post-processing steps. To reduce the costs of extensive post-processing, the process chain for AM parts has to be automated. Accordingly, robotic gripping and handling processes, as well as an efficient clamping for subtractive machining of AM parts, are key challenges. This study introduces and validates integrated bolts acting as a handling and clamping interface of AM parts. The bolts are integrated into the part design and manufactured in the same LPBF process. The bolts can be easily removed after the machining process using a wrench. This feasibility study investigates different bolt elements. The experiments and simulations conducted in the study show that a force of 250 N resulted in a maximum displacement of 12.5 µm. The milling results of the LPBF parts reveal a maximum roughness value, Ra, of 1.42 µm, which is comparable to that of a standard clamping system. After the bolt removal, a maximum residual height of 0.067 mm remains. Two case studies are conducted to analyze the form deviation, the effect of bolts on build time, and material volume and to demonstrate the application of the bolts. Thus, the major contribution of this study is the design and the validation of standardized interfaces for robotic handling and clamping of complex AM parts. The novelties are a simple and clean interface removal, less material consumption, less support structure required, and finally an achievement of a five-side tool accessibility by combining the interfaces with a three-jaw chuck.

Additive manufacturing has been adopted in many aerospace and defense applications to reduce weight and buy-to-fly ratios of low-volume high- complexity parts. Polymer-based additive manufacturing processes such as Fused Deposition Modeling (FDM) has enabled aerospace manufactures to improve the structural efficiency of parts through generative design or topology optimization. This level of design freedom did not exist in the past due to limitations associated with traditional manufacturing processes such as subtractive machining. Improvements in the material and the maturation of the FDM process has led to the production of many non-structural flightworthy parts used in aircraft today. Polymer-based additive manufacturing can be further leveraged in aerospace applications with the addition of electroplated coatings that act as reinforcement. While many of the commonly known electroplated coating applications involve enhancing the part appearance, electroplated coatings can also improve the strength, stiffness, and durability of plastic parts. Depending on the use case, the thickness of the metallic plating material (combination of copper and nickel) can be tailored to achieve the desired composite properties (metal and polymer). In this research, the tensile and flexural mechanical properties were assessed for Ultem™ 9085 FDM printed specimens and compared to specimens with metallic coating thicknesses of approximately 75-μm, 150-μm, and 300-μm. Non- destructive inspections using x-ray computed tomography were performed prior to mechanical testing to assess the electroplated coating thickness variation and overall quality.

Additive manufacturing (AM) processes, including stereolithography (SL), can fabricate complex ceramic parts layer by layer using computer-aided design (CAD) models. A ceramic slurry with high solid loading is usually used in SL to fabricate the desired shape, which is further sintered to produce the final part. The traditional SL system utilizes a tank filled with printable material, known as a vat, which for ceramic slurry contributes several limitations and operational difficulties, and further renders it non-recyclable mainly due to its high viscosity and the fragility of the green state. In this study, we utilized a continuous film supply (CFS) printer integrated with a tape casting system using in-house-designed ceramic slurry to print standard prototype specimens. Various printing parameters, including viscosity, layer thickness control, and slurry recycling efficiency, were studied. In addition, post-processing optimizations of the prototype, characterizations, and the microhardness of sintered samples were studied to determine their properties and compare them with traditional methods. The effectiveness of slurry reusability was demonstrated by printing with original and recycled slurry to produce consistent densification of final parts. Post-processing was optimized to achieve a relative sinter density of 99.02% and microhardness of 12.59 GPa. This method provides new opportunities to realize dense complex ceramic features with final properties comparable to those produced by subtractive machining and traditional SL. Furthermore, slurry recycling helps to reduce the overall cost and material consumption.

Abstract Additive manufacturing (AM), particularly laser-based powder bed fusion of metals (LPBF), enables the fabrication of complex and customized metallic parts. However, 20–40% of the total manufacturing costs are usually attributed to post-processing steps. To reduce the costs of extensive post-processing, the process chain for AM parts has to be automated. Accordingly, robotic gripping and handling processes, as well as an efficient clamping for subtractive machining of AM parts, are key challenges. This study introduces and validates integrated bolts acting as a handling and clamping interface of AM parts. The bolts are integrated into the part design and manufactured in the same LPBF process. The bolts can be easily removed after the machining process using a wrench. This feasibility study investigates different bolt elements. The experiments and simulations conducted in the study show that a force of 250 N resulted in a maximum displacement of 12.5 µm. The milling results of the LPBF parts reveal a maximum roughness value, Ra, of 1.42 µm, which is comparable to that of a standard clamping system. After the bolt removal, a maximum residual height of 0.067 mm remains. Two case studies are conducted to analyze the form deviation, the effect of bolts on build time and material volume and to demonstrate the application of the bolts. Thus, the major contribution of this study is the design and the validation of standardized interfaces for robotic handling and clamping of complex AM parts. The novelties are a simple and clean interface removal, less material consumption, less support structure required and finally an achievement of a five-side tool accessibility by combining the interfaces with a three-jaw chuck.

Abstract This paper focuses on the unconventional laser powder bed fusion (LPBF) technique in which the LPBF and machining processes were executed alternately to fabricate higher quality parts compared to those obtained using subtractive machining processes. The additional machining process changed the stress distribution inside the built part, resulting in the deformation of the surface morphology in the final part. The phenomenon pertaining to the combined LPBF and machining process based fabrication was investigated, and the influence of the process parameters on the formation of the surplus part and deformation of the machined surface was evaluated. In addition, a laser scan and machining strategy was formulated to improve the surface quality of the built part. The surplus buildup at the edge of the fabricated part occurred owing to the difference in the thermal properties between the solidified part and deposited metal powder. The laser-irradiated position at the first layer buildup and energy density were the principal factors affecting the formation of the surplus part, and the surplus buildup could be reduced using the laser scan strategy, in which the laser-irradiated position was shifted inward. The peripheral face of the built part formed periodical steps, owing to the deformation induced by the change in the thermal distribution inside the built part. These steps could be reduced using the machining strategy combining the rough machining process with a finishing allowance and stepwise finishing process.

Laser-assisted high speed milling is a subtractive machining method that employs a laser to thermally soften a difficult-to-cut material’s surface in order to enhance machinability at a high material removal rate with improved surface finish and tool life. However, this machining with high speed leads to high friction between workpiece and tool, and can result in high temperatures, impairing the surface quality. Use of conventional cutting fluid may not effectively control the heat generation. Besides, vegetable-based cutting fluids are invariably a major source of food insecurity of edible oils which is traditionally used as a staple food in many countries. Thus, the primary objective of this study is to experimentally investigate the effects of water-soluble sago starch-based cutting fluid on surface roughness and tool’s flank wear using response surface methodology (RSM) while machining of 316 stainless steel. In order to observe the comparison, the experiments with same machining parameters are conducted with conventional cutting fluid. The prepared water-soluble sago starch based cutting fluid showed excellent cooling and lubricating performance. Therefore, in comparison to the machining using conventional cutting fluid, a decrease of 48.23% in surface roughness and 38.41% in flank wear were noted using presented approach. Furthermore, using the extreme learning machine (ELM), the obtained data is modeled to predict surface roughness and flank wear and showed good agreement between observations and predictions.

In this paper, the approach and main advances made in multi-process hybrid production cells (HyProCell) for rapid individualised laser-based production are compiled and discussed, including highlights and achievements. HyProCell constructs automated manufacturing platforms that integrate highly flexible laser-based additive build processes with more conventional yet precise subtractive machining processes and include novel solutions like automatic powder removal system/machines and robot arms in integrated multi-process production cells. The HyProCell approach can either build parts additively from scratch and finish them in a coherent production single line/cell or prepare parts by machining and add laser-based additive features, achieving otherwise impossible shapes. In addition to producing new parts, existing parts can be repaired or improved by adding new details with the HyProCell hybrid concept. The research work includes the design of pilot cell facilities, the development of the, and a new modular architecture including a middleware and integration layer to ensure automation with improved pallet handling systems. Finally, the MES and data management methodologies for future improvements and pilot facility implementation were made.

Additive manufacturing (AM) is recognized as a core technology for producing high value, complex, and individually designed components as well as prototypes, giving AM a significant advantage over subtractive machining. Selective laser melting (SLM) or electron beam melting (EBM) are two of the main technologies used for producing metal components. The powder size varies, depending on the technology and manufacturer, from 20–50 μm for SLM and 45–100 μm for EBM. One of the current barriers for implementing AM for most industries is the lack of build repeatability and a deficit in quality assurance standards. The mechanical properties of the components depend critically on the density achieved; therefore, defect analysis and detection of unfused powder must be carried out to verify the integrity of the components. Detecting unfused powder in AM parts using X-ray computed tomography (XCT) is challenging because detection relies on variations in density. Unfused particles have the same density as the manufactured parts; therefore, detection is difficult using standard methods for density measurement. This study presents a methodology to detect unfused powders in SLM and EBM-manufactured components. Aluminum and titanium artefacts with designed internal defects filled with unfused powder are scanned with XCT and the results are analyzed with VGSTUDIO Max 3.0 (Volume Graphics, Germany) software package. Preliminary results indicate that detecting unfused powder in an aluminum SLM artifact with a 9.5 μm voxel size is achievable. This is possible because of the size of the voids between the powder particles and the non-uniform shape of the particles. Conversely, detecting unfused powder in the EBM-manufactured titanium artifact is less challenging owing to the uniform spherical shape and slightly larger size of the particles.

Abstract Hybrid Manufacturing (HM) combining Additive Manufacturing (AM) and subtractive machining (SM) technologies have recently been introduced and have the potential to address the shortcomings of AM, such as the poor surface finish and requires post-processing of the support structures. One such example of an HM machine is the DMG Mori Lasertec 65. These 5-axis HM machines allow for rapid deposition of material during additive manufacturing and address the issues of feature resolution, surface finish, and tolerances by subtractive machining. Additionally, these processes allow for the creation of complex geometries not possible with standard 5-axis machining. Process planning for HM is a reasonably complex manual task and could benefit from automation. Critical steps in process planning are the decomposition of the part into additive and subtractive features, sequencing all features and assigning the tool-paths for these features. This paper presents algorithms for decomposing the part and sequencing the additive and subtractive features in an automated manner, paving the way for a fully automated system for HM. Examples of a wide range of parts demonstrating the capability of the algorithm are presented.